To solve the problem that there is a danger of destroying a gate oxide film by static electricity generated in the manufacturing process of a semiconductor device using an SOI substrate, since a single crystal substrate and a supporting substrate are electrically separated because the SOI substrate is provided with an oxide film while the SOI substrate is obtained by depositing a thick oxide film on the supporting substrate composed of single crystal silicon or the like, sticking the single crystal substrate on it further, and grinding and thinning the single crystal substrate from the opposite side of the supporting substrate.

By the extremely simple method of over-etching an insulating film 2 between a semiconductor layer 3 forming a semiconductor element and the supporting substrate 1 immediately after manufacturing the SOI substrate and connecting the semiconductor layer and the supporting substrate facing each other at the part by a metal film 15, the semiconductor layer and the supporting substrate are electrically connected, the static electricity generated in a semiconductor element manufacturing process is released to the supporting substrate, and it is remarkably effective in improving an yield.